Fabric, especially clothing, can become soiled with a variety of foreign substances ranging from hydrophobic stains (grease, oil) to hydrophilic stains (clay). The level of cleaning which is necessary to remove said foreign substances depends to a large degree upon the amount of stain present and the degree to which the foreign substance has contacted the fabric fibers. Grass stains usually involve direct abrasive contact with vegetative matter thereby producing highly penetrating stains. Clay soil stains, although in some instances contacting the fabric fibers with less force, nevertheless provide a different type of soil removal problem due to the high degree of charge associated with the clay itself. This high surface charge density may act to repel some laundry adjunct ingredients, inter alia, clay dispersants, thereby resisting any appreciable peptization and dispersal of the clay into the laundry liquor.
A surfactant per se is not all that is necessary to remove unwanted clay soils and stains. In fact, most surfactants by themselves in water are surprisingly poor at removing clay soils from fabric, not all surfactants work equally well on all types of stains. In addition to surfactants, polyamine-based hydrophilic soil dispersants are added to laundry detergent compositions to “carry away” clay soils from the fabric surface and to stabilize the removed particles in solution sufficiently to minimize the possibility that the clay soil will be re-deposited upon the fabric. However, unless the clay can be initially removed from the soiled fabric, especially in the case of hydrophilic fibers, inter alia, cotton, there will be nothing in solution for the dispersants to bind to and keep suspended.
There is a long felt need in the art for laundry detergent compositions which can effectively break up and remove embedded clay and other hydrophilic soils from fabric. In addition, as the concentration of hydrophilic soil increases in the laundry liquor, there is a need for a surfactant system which will be able to handle this increased soil load. Also there is a long felt need for a clay soil active adjunct ingredient which can be optimized to fit the particular laundry detergent embodiment, inter alia, granular, liquid, and which can be therefore tailored to match the surfactant system. There has further been a long felt need for a method for cleaning hydrophilic soils from fabric wherein the hydrophilic soils are effectively peptized, dispersed, and suspended in the laundry liquor.